The preparation and reactions of a new glycoside: 2′-chloroethyl β-D-fructopyranoside

Abstract

Reaction of D-fructose with 2-chloroethanol containing hydrogen chloride at room temperature afforded highly crystalline 2′-chloroethyl β-D-fructopyranoside (4) in > 90% yield. The chloro substituent has been substituted by various nucleophilic anions (N₃^–, NCS^–, AcS^–, BzO^–) and reaction of the glycoside with base afforded the spiro-internal glycoside 1,2-O-ethylene-β-D-fructopyranose (7) in high yield. Tritylation of the glycoside (4) afforded the 1-O-trityl ether in about 50% yield whereas selective mesitylenesulphonylation gave the 1,4-disulphonate as the major product with the 1-sulphonate being isolated in only low yield. When the 1,4-disulphonate was treated with base the 4-sulphonyloxy group was selectively displaced to give the epoxide, which on more prolonged reaction afforded 4,5-anhydro-2,3-O-ethylene-1-O-mesitylenesulphonyl-β-D-fructopyranose (31) in high yield. Ring-opening of these epoxides by anions revealed that they proceeded in an anti-Furst–Plattner fashion. Reaction of the 2′-chloroethyl glycoside with triphenylphosphine and carbon tetrachloride gave 2′-chloroethyl 5-chloro-5-deoxy-α-L-sorbopyranoside in high yield.